Artificial eyes have seen little change over the years. Originally made from glass, craftspersons began using synthetic materials during World War II. Since then, the basic method of making artificial eyes has remained the same. Since the 1950's, materials such as methyl methacrylate have been used to make the artificial eyes. An example of this type of eye can be found in U.S. Pat. No. 2,551,781. Typically, an artificial eye is made in steps: the body of the eye is formed; a colored iris is painted on, or other wise attached to a flat-surfaced "button"; the iris button is attached to the body of the eye; and then an artificial cornea is sealed over the assembly.
The most difficult part of making an artificial eye is the iris. Humans have multicolored irises that can vary significantly. To achieve realistic color matching, the iris is typically painted onto the iris button. This is painstaking work that involves considerable artistic skill. Several U.S. patents discuss using photographs in lieu of painting the iris. In this technique, a photograph can be taken of a person's remaining eye and the iris can be developed from that photograph, cut, and attached to an iris button. Examples of this technique are found in U.S. Pat. Nos. 2,580,583, 2,603,791, 2,603,792, and 5,026,392. Although these patents teach using photographs to color the irises, two problems exist that have prevented extensive use of photographs for irises. First, although photographs can accurately depict the color of a human iris, when the photograph is placed under the artificial cornea, the colors are sometimes distorted. As a result, complex developing techniques must be used to develop the photographs to correct for this distortion before the cornea is installed. Obviously, this may require several tries before a close match is reached. Such experimentation is expensive and, therefore, is limited in usefulness.
The second problem is more difficult. To complete the formation of an artificial eye, the cornea is fastened to the eye body using adhesives that have strong solvents. Moreover, the adhesive must be cured while the cornea is under pressure. A small clamp vice is used for this part of the process. The solvents are strong enough to dissolve the photographic image of the iris that is attached to the iris button. In its softened state, the photographic image is susceptible to smearing as the cornea is being compressed by the clamp vice. Obviously, only a slight amount of smearing is enough to ruin the artificial eye, thereby requiring the maker to begin again.
For these two primary reasons, the use of photographs for irises in artificial eyes has remained more theory than practice.